The recovery of heat from the wastewater of buildings has been hampered, at least in part, by the fact of large solids, such as those from the toilet, which prevents wastewater passage through a reasonably sized heat exchanger. This has led to the requirement of replumbing existing buildings to provide separate drain for the toilet. Such costly undertaking, if it in fact can be done at all, i.e., apartment buildings, has prevented widespread recovery of the heat from wastewater. This, in turn, wastes vast amounts of energy which could be used to preheat fresh cold water entering a building's water heater. Moreover the waste of energy contributes to cost of living, pollution and peak period production and distribution costs of energy since hot water is known to be used by the majority of people in a given time zone, for short periods of time at the same time-of-day, i.e., morning, noon and evening.